Why we Dream and the Role of Sleep, Circadian Rhythms and The Body Clock

Scientists often give bacteria an electric shock in the lab in order to encourage them to take up extra pieces of DNA, called plasmids, which are used in genetic engineering experiments. But now, according to French researchers, lightning achieves the same feat. Timothy Vogel and Pascal Simonet, from Lyon, subjected common ground-dwelling bacteria to artificial lightning strikes. Any bacteria close to the site of the strike are obviously fried, but those further away receive a milder shock that encourages them to pick up pieces of DNA 'bait'. So far the experiments have worked with laboratory strains of E. coli, and another common bug called Pseudomonas. The researchers think that the process is widespread and helps bacteria to evolve by enabling them to scavenge pieces of DNA, containing foreign genes, from their surroundings. It may also have helped to kick-start the evolution of some of the first bacteria.Article by Jemima Stockton about probiotics and 'friendly bacteria'

生物钟由一小群神经cells sitting in the hypothalamus, which forms the base of the brain. This group of a few thousand nerve cells switch on and off groups of genes in a feedback loop lasting 24 hours. The expression of these genes alters the activity of the nerve cells which therefore effectively 'keep time'. The time registered by the body clock is then used to control the release of other hormones which are concerned with preparing us for activity or rest respectively, and in controlling the parts of the brain involved with alertness and arousal.

Luckily we don't suffer permanent jetlag when we go abroad because the clock can be reset by exposing our eyes to light. A small number of nerve fibres from a specialised group of light-responsive cells in the retina feed in to the body clock and can adjust the rhythm, according to whether it is light or dark, just as one would alter a wristwatch. This system allows the clock to adapt to changes in day length and the demands of modern-day living, but the system is not perfect and does not kick in immediately, which is why we feel jet-lagged after a long haul flight, or after working a night-shift.

When light from the sun shines into a raincloud, it hits a raindrop, goes inside the raindrop, reflects off the opposite inside surface of the raindrop, and then leaves from the front again. Just as in a prism, as the light leaves the raindrop it is split up into its constituent colours of the spectrum, producing the first rainbow you see. But sometimes when the light is very bright and the sky very dark you can see a second rainbow outside the first one and if you look very closely you'll see this is in fact a mirror image of the first rainbow. The reason for this is that after it has bounced off the back of a raindrop, some light is reflected back off the front of the raindrop again and repeats the whole process, completing the journey twice. As a result, when it finally leaves the front of the raindrop it emerges at a different angle and as a mirror image, producing a second rainbow outside the first.

You are lucky to have had it diagnosed because lots of people with it and are undiagnosed. People who have apnoea stop breathing, maybe hundreds of times a night, which means that your brain is regularly starved of oxygen producing symptoms of tiredness, poor concetration and irritability the next day. There is a way of treating this and that is to wear a mask which pushes air down into the lungs under pressure - maybe your doctors have told you about this - but you'd need to use this every night for life. There are two possibilities for what causes sleep apnoea: central apnoea is where the bit of the brain which tells you to breathe whilst you're asleep switches off - but this is rare. More common are problems in the throat so when you fall asleep your muscle tone goes away and your throat collapses, obstructing the airway. This is why pushing air down with a mask can help. People who have this can have surgery to correct it, but the surgery is fairly major.

Surveys have shown that about 6% of the population say that they absolutely never dream. There doesn't seem to that much difference between them and the rest of the population, but what has also been done is take some of these people and wake them up in sleep lab when they're in REM sleep. Every 90 minutes or so during your sleep the majority of people go into REM sleep, so you put these people in the lab, wire them up, and what happens is that you can wake people up during these periods of sleep when they ought to be dreaming. With most people you've got about an 80% chance of a dream being reported if you wake them up like this. Now if you're a non-reporter of dreams, that is one of the 6%, what's been found is that 0.6% of these absolutely never report a dream even if you wake them up during REM sleep, so in your case Betty, it is quite possible that you are having dreams and you just don't remember them.

嗜睡症是disorder where people fall asleep repeatedly during the day and there seems to be genetic component to this. Luckily there are drugs which can be used to treat it. There can be frightening aspects to narcolepsy, for instance people have been known to suddenly fall down as they fall asleep, or have nasty hallucinations as they fall asleep. The brain chemistry behind it is better understood now, and we do know about the genes that are linked to this. One particular chemical is a substance called hypocretin, and people with narcolepsy tend to have problems with the receptors for this brain chemical, or an abnormal form of this chemical. There are also people with 'clock' genes that give them a faster or slower body clock, but this shouldn't be mistaken for narcolepsy.